"Last Week Tonight" host John Oliver returned to Donald Trump last night -- specifically to dive deep into his plans for a "beautiful wall" along the U.S.-Mexico border.
"The border wall is one of the few policy proposals Trump has talked about in detail," Oliver began. "So, instead of mocking or dismissing it out of hand, tonight let's take a serious proposal by a serious presidential candidate seriously."
In terms of cost, Trump initially quoted his wall at $4 billion, or one-third of what he's now — however many months later — estimating might cost $12 billion.
"Donald Trump's margin of error is the entire GDP of Moldova," Oliver pointed out.
To check the accuracy of Trump's $4 billion-$12 billion quote, Oliver — with help from the Washington Post — crunched the numbers to determine the actual cost of 1,000 miles of a 35-foot-tall wall (the low-end of the GOP frontrunner's range of proposed heights, which tops out at 90 feet) built of "hardened concrete," steel and rebar. All together, conservative estimates bring the actual cost of building the wall to $25 billion, before factoring in the cost of maintenance.
And, assuming Trump successfully dupes Mexico into bankrolling the wall's construction, "the Congressional Budget Office estimates that wall maintenance costs will exceed initial construction costs within seven years, not including costs associated with vandalism," according to a Sierra Club report.
"It's a big, dumb thing that only gets more expensive over time," Oliver explained. "It's like getting a pet walrus. You think it's stupid now, wait until you learn what a bucket of sea cucumbers costs. You've not prepared for that."
Watch the full segment below: